Crystal structure and microstructure of minerals have been studied by
XRD and related to physical and chemical properties. A special attention
has been paid to phyllosilicates, biotites and muscovites, taken from
various rocks (the Papuk Mt in Croatia), and their polytypism has been
studied on the basis of Weissenberg and zero layer rotation single
crystal diffraction patterns and powder diffraction patterns. Simple
polytypes 1M, 2M1(most common) and 3T were found in biotite.
Also, more complex polytypes in biotite having 3, 4, 5, 6, 7, 8, 9, 11,
12, 13, 14, 17 (shown in attached figure, R is a 1M sub- cell)
and 20 single mica layers were detected. In a number of cases an
epitactic overgrowth of various (ordered and partially ordered)
polytypes was observed. The parameters of the 1M sub-cell of biotite,
deduced from zero-layer rotation patterns, depended on the chemical
composition and not on the particular polytype ( D. Slovenec, S.Popović,
Is it possible to differentiate with certainty the polytypes of biotite
2M1 and 1M according to their X-ray powder diffraction
patterns? Geol. vjesnik, 39 (1981) 203, Zagreb).

2.2
Institute of Mineralogy and Petrology, Faculty of Science (University
of Zagreb)

The
early days of crystallography in Croatia are, like in most other places,
intimately associated with developments in the field of mineralogy. The
Chair of Mineralogy and Geology was established in 1874, by Decree of
the Emperor (of the Austro-Hungarian Empire). Djuro Pilar started
teaching regular classes in the spring of 1875. Since then, the Chair
has undergone developments in several directions, but crystallography
certainly has remained one of its mainstream activities. After Djuro
Pilar, the Chair of Mineralogy and Geology was headed by eminent
professors, many of them members of the Academy of Sciences and Arts –
Mijo Kišpatić, Fran Tućan, Ljudevit Barić, Miroslav Tajder and Stjepan
Šćavničar. It needs to be mentioned that the first mineralogists from
Bulgaria, Georgij Bončev and L. Vankov obtained their doctor degree
under the supersvision of Djuro Pilar. Early research activities in the
field of crystallography involved morphological studies of crystals and
symmetry determinations by microscopic methods – techniques which are
somewhat unrighteously neglected these days. Optical crystallographic
methods were later developed and applied for the deteremination of
minerals and other crystalline substances. Ljudevit Barić made
significant contributions to the development of these methods and
teaching them to students. Scientific progress in the fields of physics
and chemistry was followed by the introduction of X-ray methods of
analysis. The equipment consisted of reflexion goniometers, polarizing
microscopes, X-ray diffraction cameras, modern diffractometers and
electron microscopes. Stjepan Šćavničar contributed significantly to the
development and application of crystallographic methods, particularly in
the field of crystal structure determinations of stibnite and a series
of synthetic compounds. From 1955 onwards he headed crystallographic
research at the Institute and procured equipment ranging from early
X-ray generators and cameras to a modern powder diffractometer. His work
in experimental mineralogy resulted in the late 50-ies of the 20th
century in one of the first successful hydrothermal synthesis of beryl.
He taught mineralogy and chemistry many generations of students,
supervising numerous masters and doctoral theses. This modern
instrumentation is nowadays still used for crystallometric measurements,
although in the process of determination of new minerals and a better
characterisation of existing ones. Such research involves the
implementation of powder- and single- crystal diffractometry and
electron microscopy, but also thermal methods of analysis, Raman and IR
spectrometry and microanalysis. More than 10 new minerals have been
identified and determined in the Institute of Mineralogy and Petrology.
This type of resarch invloves the application of complex investigation
methods, resulting in precise determinations of crystallographic data
including crystal morphology, structure, physical properties such as
optical constants, specific gravity, hardness, cleavage and specific
ones such as electric or magnetic properties. Chemical information is
always used to determine the chemical composition and formula of the
investigated materials, as well as for genetic considerations and
thermodynamic stability issues. Our researchers therefore closely
collaborate with investigators in associated fields. New areas of
research include experimental mineralogy, biomineralization processes
and environmental mineralogy. Today, professors Vladimir Bermanec and
Darko Tibljaš are leading researchers in the field of crystallography,
educating not only younger colleagues at the Institute but also
collaborating closely with researchers in Croatia, Macedonia, Slovenia,
Bosnia and Hercegovina, Austria, Hungary, Canada, Brasil and Russia.